Magnetic amplifier and self-modulator



Oct. 11, 1927. 1,645,301

J. SLEPIAN MAGNETIC AMPLIFIER AND SELF MODULATOR Filed April 21, 1921WITNESSES: INVENTOR Jose 0f? Slep/an.

if M

ATTORNEY Patented 041.11, 1927.

' UNITED STATES PATENT o-Fnca.

JOSEPH SLEPIAN, OF WILKINSBUBG, PENNSYLVANIA, ASSIGHOB TO WIBTDIGEOUIIELECTRIC & MANUFACTUBIHG COMPANY, A CORPORATION OF PENNSYLVANIA.

MAGNETIC MIDI FEB AND SELF-KODULATOB,

Application med April :1, 1921. 8er1a1Ko..488,208.

My invention relates to wireless systems and more especiall toelectrical systems which may be emp oyed either to amplify or tomodulate the variable currents employed in wireless telegraph ortelephone systems.

One object of my invention is to rovide an amplifying system which isnot imited to the amplification of relatively small amounts of power breason of inherent limitations in the design thereof.

Another object of my invention is to provide simple and eflicient meanswhereby the undamped oscillations in sustained current-- transmittingsystems ma be periodically modulated to admit of t eir rece tion byreceiving stations which are unab e to receive undamped signals.

Other ob'ects will be apparent from the following description, taken inconnection with the accompanying drawings.

Heretofore, in systems of amplification, it has been possible to amplifyonly relatively small amounts of power by reason of structural andtheoretical limitations in the amplifying devices employed.

Furthermore, in the art of signaling, it has been customary, in stationsemploying sustained oscillating currents, to communicate with receivinstations unable to receive the undampe signals radiated therefrom byemploying a special spark transmitter.

According to my invention, I provide an electrical system which may beemployed, with slight modifications in the design thereof, either as anamplifier system for amplifying large amounts of power or as aselfmodulating) system for producing audiblefrequency eats or groups ofradiated waves in contmuous-wave, wireless-transmission systems.

In my coending application, Serial No. 463,209, file April 21, 1921, Ihave shown a purely electromagnetic system for accomplishing the desiredresult-s. In the application just mentioned, the system comprises acircuit having radio-frequency currents therein and a magnetizingwinding, a circuit having audio-frequency currents therein and amagnetizing winding, a common.

magnetizable core member associated with said magnetizing windin s,reactance devices resonant to said ra io-frequency our- 5 rents includedin said first-named circuit for causing the modulations of theradiofrequency currents tolag the modulating audio-frequency'currents.

In the system 'ust described, it was found that, if the osses in theaudio-flew quency circuit were sufficiently small, the effect of the lagbetween the modulations of the radio-frequency circuit and the modulatmgaudio-frequency circuit is to cause a transfer of energy from theradio-frequency circuit to the audio-frequency circuit tending tomaintain the currents in the'latter circuit without additionalaudio-input. Thus, the system may easily become selfmodulating. I

It was further found that if the system were soadjusted that it was onthe point of sustaining the currents in the audiofrequency circuit,small changes inthe value of the audio-input 'efi'ect relatively largechanges in the value of the radio-frequency currents.

I have found, however, that the desired results heretofore mentioned mayalso be obtained by emplo inga mechanical movable armature mem er whichis disposed between two small electromagnets; one of which is excited bythe audio-frequency currents and the other of which is excited by theradio-frequency currents.

My invention may best be understood by reference to the accompanyingdrawings, in which:

Fig. 1 is a diagrammatic view of circuits and apparatus embodying myinvention.

' Figs. 2, 3 and 4 are curve diagrams illustrating the fact that, withthe radio-frequency circuit in a nonresonant state, substantially nomechanical work is done by the force upon the armature due to theradio-frequency currents.

Fig. 5 1s a curve diagram illustrating the fact that, with theradio-frequency circuit resonant to the radio-frequency currentstherein, the currents'just mentioned will do mechanical work upon thearmature tending to sustain its motion.

Referring to Fig. 1, a radio-frequency circuit 1 is 'operativelyconnected to a local source of radio-frequency currents 2 throughcoupling coils 3 and 4, and to an audio-frequency circuit 5 through amagnetic device 6.

The source of energy 2 is shown comprising an are 7, which is shunted bythe coup coil 4 and a condenser 8. It is understoo however, that minvention 7 is not to be limited to the particular t pe of oscillationgenerator shown in the rawings, as other sources of radio-frequency orultraaudio-frequcncy currents may be employed.

The u magnetiza le members 12 and 13 carrying .windin 9 and 11respectively, which are include ,res ctivel ,in the ra 'o-frequencycircuit 1 an in the audio-frequency circuit 5. Flexibly mounted betweenthe magnetiz'able members 12 and 13 is an armature member 14 which maybe secured to a supporting member 15 by means of'a flexible memberorspring 16, and is so disposed between the magnetizable members 12 and13' that it ma periodically vary the self-inductance 0! the coil 9.. Thenatural period of the s ring 16, with the armature 14 attached t ereto,is preferably resonant to the frequency of the audio-frequency currentsin circuit 1.

The audio-frequency circuit 5 may comprise one or more of the followingelements: a source of audio-frequency, such as a detector device forincoming signals (not shown); a coupling coil 17, which is associatedwith a pair of feed-backcoils 18 and 19 hereinafter mentioned; and aninductance coil 21 and a condenser 22 for tuning the circuit to theaudio-frequency currents.

The radio-frequency circuit 1 is shown as comprising the coupling coil3, the winding 9,-an inductance coil 23 and a condenser 24 for tuningthe circuit to resonance with the source of energy 2; and a pair ofrectifier circuits 25 and 26 which are connected in shunt to each otherand in series relation in the circuit 1. The rectifier circuits 25 and26 include, respectively, indicating devices 29 and 31 shown as a air oftelephone receivers and the opposite y connected rectifiers 27 and 28.The indicating devices 29 and 31 may be shunted also by the feed-backcoils 18 and 19, which are connected in opposition, as shown.

The magnetizable members 12 and 13 are preferably operated upon thelinear portion of the magnetization curve. 7

The curve diagrams shown in Figs. 2, 3 and 4 explain the fact that, ifthe radio-frequency circuit 1 were non-resonant to the source of energy2, the modulation of the currents therein by the audio-frequencycurrents would be eifected with just sufficient power input in theaudio-frequency circuit to supply the energy losses in the magneticdevice 6. 7

Fig. 2 is a. curve diagram showing the variations in the air-gap lengthof the magnetizable member 14, with respect to the magnetizable member12; and, for purposes of illustration, has beenrepresented in thesine-wave form.

etic device 6 inc des a pair of- Fig. 3 is curve diagram showing themodulations of the radio-frequency currents produced by theaudible-frequency variations in the reluctance of the magnetic paththrough the armature member 14 and the magnetizable member 12. In thelast-mentioned diagram, curve 32 represents the radio-freqiiliencyoscillations, and curve 33 represents t e audio-frequency modulationthereof. Neglecting the slight lag, equalto a small fraction of theradio-frequency period, which would be caused by hysteresis, it isevident that the mean pull upon the armature 14, that is caused by theradio-frequency currents is in phase with the modulations 33 and it hasbeen so illustrated in Fig. 4.

l rom the foregoing curve diagrams, it may readily-be seen that thecurve representing the mean pull upon armature 14 is in phase with thecurve representing the variations in the air-gap length, and, therefore,in gadrature with the velocity of the armature.

ence, no mechanical work is done by the radio-frequency currents uponthe magnetic device 6 under the conditions assumed. The audio-input,therefore, is required to supply only the losses in the magnetic device6, in order to modulate the radio-frequency currents. v

I have found that, by adding a seriesresonant device, such as thatindicated at 23,24, tuned to resonance with the radio-frequencycurrents, the modulations of the radio-frequency currents are caused tolag behind the modulating audio-frequency currents, as indicated in thecurve diagram shown in Fig. 5.

The reason for the lag produced by the addition of the series-resonantreactance device will probably be best understood by av consideration ofthe energy-stored by the device. If an oscillatory electromotive forceof constant amplitude is suddenly impressed upon an oscillatorycircuitcontaining a series-resonant device, the currents will not immediatelyreach a steady value, since the energy stored in the resonant devicemust be supplied from the source; but the amplitude of the oscillationswill gradually increase for a number of cycles, dependent upon the ratioof the stored energy to the resistance load, as is well known. Similarlyif the oscillatory electromotive force is decreased in amplitude, orwithdrawn altogether, the excess energy stored in the reactance deviceswill cause the corresponding modulation of the currents to be postponedto a time which may be a number of cycles later.

The result of such lag in the present device is that the modulationshave a component in phase with the movements of the armature. as well asa component displaced 90 thereupon. It will be seen that thefirstmentioned component tends to maintain the movements of thearmature, and that energy is thus supfilied to .the audio-frequencycircuit from t in%to reduce the aha-z: ry audio input.

- y sufiiciently reducing the in the audio-frequency circuit, enoughpower, may be supplied thereto from the radio-frequency circuit tomaintain the currents therein without additional audio-frequency input.The system then becomesa self-modulator.

I have found that my system is most efiicient as an amplifier. upon theadjustment of the inductance coil 23 and the condenser 24 to such valuethat the system is on the oint of sustaining currents in circuit 5.dditional amplification may be obtained through the feed-back coils 18and 19 and the coupling coil 17, said coils feeding back the audio-ireuency modulation of currents in the ra io-freauency circuit 1.

Assuming ra io-frequency currents su plied to the radio-frequencycircuit 1 y means of the source of radio-frequency energy 2, the effectof impressing currents of an audible frequency upon circuit 5 is toeffect the modulatlon of the radio-frequency currents in circuit 1 atfrequencies corresponding to those in the audio-fr uency clrcuit 5, allas hereinbefore describe The effect of the rectifiers 27 and 28 is torender audible, in the indicating devices 29 and 31 the notecorresponding to that of the audiorequenc modulations.

The self-mo ulating characteristic of my system is of particularimportance in marine work in that iteliminates the spark transmitterswhich have heretofore been considered necessary in continuous-wavesystems when desiring to communicate with receiving systems responsiveonly to energy radiated by s ark transmitters.

Another a vanta e of my invention resides in the fact t at it embodiesmeans whereby reception of signal impulses may be efiected fromcontinuous wave systems without heterodyning the received energy.

Still another advantage of my invention resides in the provision of amagnetic amplifying system wherein relatively small or large amounts ofpower may be efficiently am lified.

ile I have shown only one embodiment of my invention, in which theinductance of a circuit is mechanically varied, it is obvious that amechanically varied condenser may be equally as well employed withoutdeparting from the s irit and scope of my invention. I desire, terefore, that only such limitations shall be imposed thereon as are setforth in the appended claims.

I claim as my invention:

1. In a magnetic amplifier, a circuit having radio-frequency currentstherein and a magnetizi winding, 8. second circuit having audiorequencya magnetizing winding, a magnetlzable meme radio-frequency circuit,tendcurrents therein and her so dis d "that the resultant motion thereocauses cha es in the inductance of the radio-frequency circuits, wherebthe radio-frequency currents may be mod ated at frequenciescorresponding to the audiofrequency currents. Y

2. In a ma etic amplifier, a circuit-havmg sustain oscillating. currentstherein and a magnetlzing winding, a circuit having aud o-frequencycurrents therein and a magnetizin wlnding, a ma etizable member adap torespond to t e magnetic fields set up by currents in said magnetizinwindings, w ereby the currents in 'sai firstnamed circult may bemodulated at frequencles corresponding to those in said second-namedcircuit.

3. In a ma netic amplifier, a circuit havmg sustaine oscillatin currentstherein and a magnetizing win ing, a second circuit havingaudio-frequency currents therein and a magnetizing winding, magnetizablemembers for each magnetizing winding, and a vibratory magnetizablemember disposed adjacent said first and second-named magnetizablemembers. 4. In a ma netic amplifier, a circuit having sustaineoscillating currents therein and a magnetizing winding, a second circuithaving audio-frequency currents therein and a magnetizing winding,magnetizable members for each magnetizing winding, an armatureresponslve to the magnetic fields set up by currents in said first andsecond-named magnetizing windings, whereby said oscillating currents aremodulated in accordance with said audio-frequency currents and means forcausing the modulations of said oscillating currents to have such phaserelation to said audio-frequency currents that the mean pull of saidmodulated currents on said armature has a component in phase with themovement thereof.

5. In a magnetic amplifier, a resonant circuit having radio-frequencycurrents therein and a magnetizing windin a circuit havingaudio-frequency currents t erein and a magnetizing winding, magnetizablemembers for each magnetizin wlnding and a flexibly mounted magnetlzablemember responsive to the magnetic fields set up by currents in said Inetizable members, the resultant motion 0 said flexibly mountedmagnetizable member being such that the .movement thereof isapproximately in phase with the force thereon caused by saidradio-frequency currents.

6. In a magnetic amplifier, a circuit carryin audio-frequency currentstherein Y and inc udin a magnetizing winding and a coupling coi acircuit carrying radio-frequency currents therein and includin amagnetizing winding, a pair of recti ers connected in parallelopposition, an indicating device and feed-back coils associated J anwith said coupling coil, magnetizable members associated with each maetizing winding, and a flexibly mounte magnetizable member so disposedadjacent said magnetizing windings that the resultant motion thereofeffects the modulation of said radio frequency currents at a frequencycorresponding to the audio-frequency currents.

7. The combination with a source of sustained oscillations, of amagnetizing coil connected thereto, a vibratory armature associated withsaid coil, whereby the reactance of the latter is varied in accordancewith the movements of said armature, said armature I cuit havingsustained oscillating currentstherein, a second circuit havingaudio-frequency currents therein, means controlled by saidaudio-frequency currents for mechanically varying the reactance of saidfirstnamed circuit to cause corresponding modulations of the currentstherein, and auxiliary means for transferring audio-frequency power fromsaid first-named circuit to said second-named circuit.

10. A magnetic amplifier comprising a circuit having sustainedoscillating currents therein, a second circuit having audio-frequencycurrents therein, means controlled by said audio-frequency currents formechanically varying the reactance of said first named circuit to causecorrespond' modulations of the currents therein, a rectifier for saidoscillating currents, and means for transferring audio-frequency powerfrom said rectifier currents to said audio-frequency circuit.

11. The method of varying the reactance of a sustainedoscillatory-current circuit b means of a tuned vibratory member, whicconsists in so varying the phase relati0n shi between the variations insaid reactance an the resultant modulations in said oscillatory currentthat said modulations have a component in phase with the velocity ofsaid vibratory member. I

12. In a carrier-current signaling system, the combination with acarrier-current circuit thereof, of modulating means comprising aninductance device included in said circuit, a second circuit havingaudio-frequency currents therein, and movable means controlled by saidaudio-frequency currents for mechanically varying the reactance of saidinductance device to cause corresponding modulations of the currents insaid firstnamed circuit 13. In a carrier-current signalingsystem, thecombination with a carrier-current circuit thereof, of modulating meanscomprising a magnetizable-core inductance device included in saidcircuit, a movable magnetizable armature included in the magneticcircuit of said inductance device, and means for moving said armature insuch manner as to vary the inductance of said device in response to asignal or signals to be transmitted.

In testimony whereof, I have hereunto subscribed my name this 14th dayof April, 1921.

JOSEPH SLEPIAN.

